This sealant achieves all test-verified STC/MTC by sealing gaps in partitions with a long-lasting, resilient, acoustical seal. Sheetrock® Brand Acoustical Sealant is water-based, highly elastic and easy to apply with hand-gun equipment to vertical and horizontal surfaces (even overhead) without sagging. Sheetrock® Brand Acoustical Sealant is excellent for fire-rated partitions and acceptable for use at the perimeter of wall assemblies rated 1-3 hours.